Thus far, ultrasonic wave generation apparatuses have been used in rangefinding techniques and the like that employ ultrasonic waves.
For example, Patent Document 1, indicated below, discloses an ultrasonic wave generation apparatus that uses a piezoelectric vibrator. This ultrasonic wave generation apparatus includes a housing and an ultrasonic wave generation element disposed within the housing. The ultrasonic wave generation element has a frame body and plate-shaped first and second piezoelectric vibrators. A groove or a through-hole is formed in a central area of the frame body. To close off the groove or through-hole, the first piezoelectric vibrator is bonded to a first main surface of the frame body and the second piezoelectric vibrator is bonded to a second main surface that is opposite to the first main surface. The first piezoelectric vibrator and the second piezoelectric vibrator vibrate at opposite phases from each other, and as a result, the ultrasonic wave generation element vibrates in a buckling tuning-fork vibration mode. The ultrasonic wave generation apparatus disclosed in Patent Document 1 emits ultrasonic waves generated by the vibration of this ultrasonic wave generation element.
On the other hand, Patent Document 2, indicated below, discloses an electroacoustic transducer that uses a support body having a hollow structure. In this electroacoustic transducer, a part of each of main surfaces of the support body is constituted by an elastic material. Piezoelectric elements are bonded to outer side portions of the parts of both main surfaces of the support body that are constituted by the elastic material. In addition, an acoustic emission opening is formed in a side surface of the support body. This acoustic emission opening is formed as a through-hole that makes an inner space of the support body communicate with the exterior.
Patent Document 1: WO2012/026319
Patent Document 2: Japanese Unexamined Patent Application Publication No. 2011-228966